1. Field of the Invention
This invention relates to new and useful improvements in earth drill bits and to methods of assembling such bits.
2. Brief Description of the Prior Art
Roller bits, and particularly three cone roller bits, are well known in the prior art. J. E. Brantly in History of Oil Well Drilling, 1971, Gulf Publishing Co. devoted a very long chapter to the history of development of rotary bits.
The patent literature on roller cone bits is quite prolific on the development of new and improved drill bits through the years. The literature and patents on the manufacture and assembly is not quite so well developed, perhaps because many improved manufacturing techniques are practiced in secret rather than being patented or published.
The preparation of three cone bits by forming the bit body in three separate body segments and welding them together is well known. Brown U.S. Pat. No. 2,831,661 shows one such method of manufacture and assembly. References cited in the Brown patent and other more recent patents shown various methods of manufacture and assembly. The manufacturing process generally used today is one where the bit body is formed in three separate segments including one third of the hollow pin portion, the shank, the depending leg, the inturned bearing journal, and, sometimes, the hollow legs or projections containing the nozzles used in flushing out spoil or cuttings produced in drilling. The three segments are fitted together lengthwise and welded along longitudinal seams. The surface is machined or ground smooth in the welded areas and the entire surface finished off. The hollow pin is then threaded with an API regulation thread or other approved thread and the assembly of the various components completed. This manufacturing operation is lengthy and quite expensive.
The present invention comprises an improved method of assembly of the drill bit body sub-assembly and of the completed bit including the roller cones. The method is considerably simpler than the ones in commerical use today and requires a minimum of finishing operations.